Polishing apparatus, polishing method and method of manufacturing semiconductor device

ABSTRACT

There is disclosed a polishing method which comprises positioning a treating substrate held by a substrate holder over a turntable so as to enable the treating substrate to press-contact with a polishing region of a polishing surface of the turntable, the polishing surface having the polishing region where the treating substrate moves relative thereto, and a non-polishing region surrounded by the polishing region, introducing a first liquid and a second liquid into a slurry mixing section disposed at the non-polishing region of the polishing surface, at least one of the first and second liquids containing an abrasive component, and applying a mixed slurry comprising the first and second liquids which have been mixed together in advance in the slurry mixing section to the polishing surface while rotating the turntable to enable the treating substrate to move relative to the polishing region, thereby polishing the treating substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-190659, filed Jun. 28, 2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a polishing apparatus, polishing method, and to a method of manufacturing a semiconductor device. In particular, the present invention relates to a polishing technique employed in forming a damascene wiring of Cu, W, Al, etc., which is designed to be mounted on a DRAM or a high-speed logic LSI, or for planarizing an insulating film.

[0004] 2. Description of the Related Art

[0005] In recent years, in order to meet the sophistication in the manufacture of semiconductor elements or to meet an increased refinement of semiconductor elements, novel manufacturing apparatuses are now being developed. Among them, a CMP (Chemical Mechanical Polishing) apparatus is one of the apparatuses indispensable in the fabrication of an buried structure such as buried metal wirings, buried element isolations, etc.

[0006] Meanwhile, in a process employing this CMP apparatus, one of the main goals is to enhance the polishing speed, to promote the throughput of polishing. Generally, for polish a metal such as Cu, a slurry containing an oxidizing agent is employed to denature the polishing surface into an oxide surface which can be easily polished, thus enhancing the polishing speed of the metal. However, the oxidizing agent in a slurry is subject to decomposition or reaction due to the changes in natures thereof with time, and may give rise to coalescence or dissolution of abrasive grains. In this case, various problems such as deterioration of polishing speed and increase in number of scratches may be caused.

[0007] With a view to avoid the aforementioned problems accompanied with the employment of an oxidizing agent, a method has been tried in which a slurry containing the oxidizing agent is kept separately from a slurry containing abrasive grains, until these two slurries need to be mixed together, immediately before using them for polishing. Usually, in two-part supply systems, two slurries kept separately are mixed together immediately before they are fed drop-wise, as a single liquid, onto a polishing surface. For example, two slurries are fed to a polishing surface by a specific supply system, such as a T-shaped supply or F-shaped. However, a polishing apparatus employing any of these supply systems has a drawback in that since the flow rate of slurries, as well as the length of pipeline are restricted, it is difficult to sufficiently uniformly mix together two slurries, especially when an additive which cannot mix with these slurries, such as a nonionic surfactant or a high-hydrophobicity oxidation inhibitor, is present.

[0008] As mentioned above, even though it may be meaningful to keep a slurry containing an oxidizing agent by separating it into a two-part supply system in order to avoid the deterioration of stability thereof, it may be difficult to derive the inherent characteristics of the slurry in a stable manner unless two chemical liquids constituting the two-part system are uniformly mixed on the occasion of using them for polishing a substrate to be polished (i.e. polishing substrate).

[0009] In view of the stability of slurry, the chemical liquids which are separately stored should preferably be mixed together as close to the time of use as possible. Further, in order to make it possible to use a slurry immediately after the mixing thereof, the provision of an auxiliary supply facility for mixing is not appropriate.

BRIEF SUMMARY OF THE INVENTION

[0010] A polishing apparatus according to one embodiment of the present invention comprises:

[0011] a turntable having a polishing region where a treating substrate moves relative thereto, and a non-polishing region surrounded by the polishing region;

[0012] a substrate holder holding the substrate, thereby enabling the substrate to press-contact with a polishing surface located within the polishing region;

[0013] a first supply pipe feeding a first liquid;

[0014] a second supply pipe feeding a second liquid; and

[0015] a slurry mixing vessel disposed above the turntable within the non-polishing region and away from the tip ends of the first supply pipe and the second supply pipe, the slurry mixing vessel storing and mixing the first and second liquids to obtain a mixed slurry and to feed the mixed slurry onto the polishing surface.

[0016] A polishing method according to one embodiment of the present invention comprises:

[0017] positioning a treating substrate held by a substrate holder over a turntable so as to enable the treating substrate to press-contact with a polishing region of a polishing surface of the turntable, the polishing surface having the polishing region where the treating substrate moves relative thereto, and a non-polishing region surrounded by the polishing region;

[0018] introducing a first liquid and a second liquid into a slurry mixing section disposed at the non-polishing region of the polishing surface, at least one of the first and second liquids containing an abrasive component; and

[0019] applying a mixed slurry comprising the first and second liquids which have been mixed together in advance in the slurry mixing section to the polishing surface while rotating the turntable to enable the treating substrate to move relative to the polishing region, thereby polishing the treating substrate.

[0020] A method for manufacturing a semiconductor device according to one embodiment of the present invention comprises:

[0021] forming an insulating film above a surface of a semiconductor substrate;

[0022] forming a recessed portion in the insulating film;

[0023] depositing a conductive material in the recessed portion as well as above the insulating film, to form a conductive layer; and

[0024] removing the portion of the conductive material that has been deposited above the insulating film outside the recessed portion to leave the conductive material in the recessed portion;

[0025] wherein at least part of the conductive material deposited above the insulating film is removed by:

[0026] positioning the semiconductor substrate held by a substrate holder over a turntable so as to enable the semiconductor substrate to press-contact with a polishing region of a polishing surface of the turntable, the polishing surface having the polishing region where the semiconductor substrate moves relative thereto, and a non-polishing region surrounded by the polishing region;

[0027] introducing a first liquid and a second liquid into a slurry mixing section disposed at the non-polishing region of the polishing surface, at least one of the first and second liquids containing an abrasive component; and

[0028] applying a mixed slurry comprising the first and second liquids which has been mixed together in advance in the slurry mixing section to the polishing surface while rotating the turntable to enable the semiconductor substrate to move relative to the polishing region, thereby polishing the conductive material.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0029]FIG. 1 is a schematic diagram illustrating the construction of polishing apparatus according to one embodiment of the present invention;

[0030]FIGS. 2A to 2C are cross-sectional views each illustrating the manufacturing process of semiconductor device according to another embodiment of the present invention;

[0031]FIG. 3 is a graph illustrating the dependency of the polishing rate of Cu on the number of wafers;

[0032]FIG. 4 is a schematic diagram illustrating the construction of polishing apparatus according to the prior art;

[0033]FIG. 5 is a schematic diagram illustrating the construction of polishing apparatus according to the prior art; and

[0034]FIG. 6 is a schematic diagram illustrating the construction of polishing apparatus employed in a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Next, embodiments according to the present invention will be explained in detail with reference to drawings.

[0036]FIG. 1 is a schematic diagram illustrating the construction of polishing apparatus according to one embodiment of the present invention. As shown in FIG. 1, a turntable 11 has a polishing cloth 13 adhered on the upper surface thereof and is designed to be revolved horizontally about the central axis 12 thereof in the direction indicated by an arrow. The revolving speed of the turntable on this occasion may be within the range of about 30 to 150 rpm. Over the top surface of the turntable 11, there is disposed a top ring 14 serving as a substrate holder for holding a semiconductor wafer 16. This top ring 14 is designed to be revolved horizontally about the central axis 15 thereof in the same direction as that of the turntable 11. This top ring 14 is enabled to revolve at a revolving speed of about 30 to 150 rpm. During the revolution of this top ring 14, a semiconductor wafer 16 held by the top ring 14 is pressed against the polishing cloth 13 at a polishing load of 50 to 700 g/cm², thereby polishing the semiconductor wafer 16.

[0037] More specifically, as the turntable 11 is revolves, the semiconductor wafer 16 held by the top ring 14 is moves along a circular orbit over the polishing cloth 13 and relative to the polishing cloth 13, thereby polishing the semiconductor wafer 16. A region of the polishing cloth 13 which is located on the inner peripheral side of this circular orbit may be considered as a non-polishing region, which has nothing to do with the polishing of the semiconductor wafer 16.

[0038] In this non-polishing region, there is disposed a slurry mixing vessel 17 functioning as a slurry mixing section in which a first liquid 20 and a second liquid 21 can be stored and mixed with each other to create a mixed slurry which is subsequently fed onto the polishing cloth 13. The first liquid 20 may be a chemical dispersion liquid containing abrasive grains for example, while the second liquid 21 may be a chemical liquid containing an oxidizing agent for example. This first liquid 20 can be stored in a first storage tank 18 and then fed through a pump 22 and a first supply pipe 24 to the slurry mixing vessel 17. On the other hand, the second liquid 21 can be stored in a second storage tank 19 and then fed through a pump 23 and a second supply pipe 25 to the slurry mixing vessel 17. These two kinds of liquid may be introduced respectively into the slurry mixing vessel 17 at a flow rate of 50 to 500 mL/min for example. If desired, it is also possible to provide the aforementioned slurry-feeding system with a third storage tank for storing a third liquid containing other kinds of components, with a pump for feeding this third liquid and with a third supply pipe.

[0039] The first liquid 20 and the second liquid 21 that have been introduced into the slurry mixing vessel 17 are sufficiently uniformly mixed together through the effects of the supply pressure and convection of these liquids, as well as through the effect of rotation of the turntable, before these liquids are finally applied to the surface of the polishing cloth 13 through the overflow thereof.

[0040] Accordingly, the size of the slurry mixing vessel 17 should such that it is large enough to accommodate the two kinds of liquid fed thereto, and to carry out mixing of them, but small enough to be placed within the non-polishing region of the polishing cloth 13. For example, the size in the lateral direction of the slurry mixing vessel 17 may be within the range of 10 mm to 60 mm. If the slurry mixing vessel 17 is too small, it may become difficult to accommodate the two liquids being fed thereto and to carry out sufficient mixing of them. On the other hand, if the slurry mixing vessel 17 is too large, it may become impossible to install the slurry mixing vessel 17 within the non-polishing region of the polishing cloth 13. Thus, if the size of the slurry mixing vessel 17 is not suitably selected, the fundamental function of the polishing apparatus to polish a wafer may be severely compromised. Further, the height of the slurry mixing vessel 17 should preferably be within the range of 1 mm to 40 mm. If the height of the slurry mixing vessel 17 is too low, it may become difficult to accommodate the two liquids being fed thereto and to sufficiently carry out the mixing of them. On the other hand, if the height of the slurry mixing vessel 17 is too high, an excess amount of abrasive grains may remain in the slurry mixing vessel 17, or the slurry mixing vessel 17 may interfere with the first supply pipe 24 or with the second supply pipe 25. In view of these problems, the height of the slurry mixing vessel 17 should be determined in such a way that the brim of the slurry mixing vessel 17 be positioned lower than and spaced away from the tip end of the supply pipes 24 and 25, while taking the capacity of the slurry mixing vessel 17 into consideration.

[0041] In order to perform uniform mixing of these two kinds of liquid supplied, and to enable the resultant mixture to overflow onto the polishing cloth 13, the slurry mixing vessel 17 is preferably cylindrical. Of course, there is no particular limitation with regard to the configuration of the slurry mixing vessel 17.

[0042] The slurry mixing vessel 17 may be manufactured from a plastic material for example. On the occasion of positioning the slurry mixing vessel 17 at the non-polishing region of the polishing cloth 13, the slurry mixing vessel 17 can be secured to the surface of the polishing cloth 13 by using a double-sided adhesive tape or screws. If screws are used for the positioning of the slurry mixing vessel 17, the positioning of the slurry mixing vessel 17 can be more reliably performed by fixing the slurry mixing vessel 17 to the turntable 11 with the polishing cloth 13 therebetween. As long as the slurry mixing vessel 17 is positioned within the non-polishing region and the slurry mixing vessel 17 is enabled to receive the two kinds of liquid being supplied, there is no particular limitation with respect to the location of the slurry mixing vessel 17. Namely, the slurry mixing vessel 17 is not necessarily positioned coaxial with the center of the polishing cloth 13.

[0043] In the polishing apparatus according to this embodiment of the present invention, a slurry which necessitates separate storage for maintaining the storage stability can be dealt with. One example of such a slurry is a slurry used in a Cu-CMP procedure. A slurry used in a Cu-CMP procedure is usually separated, in view of enhancing storage stability, into an abrasive grain-containing dispersion liquid, and a solution containing an oxidizing agent. As for the oxidizing agent useful in this case, there has been employed ammonium persulfate, which takes a relatively long time before it becomes compatible with the liquid, as compared with hydrogen peroxide which is generally employed as an oxidizing agent. Further, in order to meet various requirements such as high polishing rate, erosion resistance, non-defectiveness, etc., the dispersion liquid containing abrasive grains may further contain an additive such as quinaldinic acid, a surfactant, etc. Since these additives are highly hydrophobic however, it has been considered difficult, according to the conventional slurry supply system, to uniformly mix the aforementioned two liquids on the occasion of using them.

[0044] Further, a slurry commonly employed in the polishing of W (tungsten) can be used in the operation of the apparatus according to this embodiment of the present invention. The slurry employed in the W-CMP procedure may contain various additives, such as colloidal silica as an abrasive grain, hydrogen peroxide (H₂O₂) as an oxidizing agent, Cu²⁺ions as a catalyst for activating hydrogen peroxide, potassium dodecylbenzene sulfonate as a surfactant for improving the planarizing characteristics of the slurry, and the like.

[0045] Although hydrogen peroxide is effective in enhancing the polishing rate of W, as the hydrogen peroxide is activated into HO* by the action of Cu²⁺ion, the life of HO* is very short, meaning that hydrogen peroxide cannot be stored as a mixture with Cu²⁺ions. Colloidal silica is liable to flocculate and precipitate due to the salting-out effect thereof as colloidal silica is contacted with Cu²⁺ion, so that colloidal silica cannot be stored as a mixture with Cu²⁺ion. On the other hand, under a specific pH region (pH=5 or less) where hydrogen peroxide cannot be decomposed, silica is potentially unstable and hence liable to flocculate and precipitate, making colloidal silica cannot be stored as a mixture with hydrogen peroxide. Therefore, the polishing slurry is generally separated, for the purpose of storage, into three kinds of liquid, i.e. an abrasive grain-containing dispersion liquid containing colloidal silica, an oxidizing agent solution containing hydrogen peroxide, and a catalyst solution containing Cu²⁺ions. On the occasion of using these three kinds of liquid, they are mixed together immediately before the polishing operation.

[0046] A metal film containing Ru or an Ru compound can be polished by using a polishing slurry which is formed of an aqueous solution containing, as an abrasive component, a cerium compound (IV) such as cerium nitrate, cerium diammonium nitrate, etc. Generally, cerium compound (IV) is stable, as it exists as a solution in high concentration. However, once cerium compound (IV) is diluted into a solution of low concentration, cerium compound (IV) is caused to change with time, thereby deteriorating the oxidizing power thereof and hence deteriorating the polishing performance thereof. Accordingly, if a polishing is to be performed by using an aqueous solution containing cerium compound (IV), the solution of cerium compound (IV) should be put to use without leaving it stand for a long period of time after the dilution thereof. More preferably, the solution of cerium compound (IV) should be used immediately after the dilution thereof, most preferably concurrent with the dilution thereof. Therefore, the cerium compound (IV) should be stored as an aqueous solution of high concentration separately to the dilution water.

[0047] Further, when ceria is used as an abrasive grain in a slurry for polishing an oxide film, a surfactant may be added to the slurry for the purpose of enhancing the planarizing characteristics of the slurry. However, when ceria particles are kept contacted with the surfactant for a long period of time, the surfactant adheres to the surface of ceria particles, thereby making it difficult for the ceria particles to exhibit the inherent characteristics thereof. Therefore, it is desirable to separate the slurry into two liquids, i.e. an abrasive grain-containing dispersion liquid containing ceria as an abrasive grain, and a liquid containing a surfactant, these two liquids being subsequently mixed together immediately before using them for a polishing procedure.

[0048] Generally speaking, when a dispersion containing abrasive grains is stored as a solution of high concentration, it can be stored without generating the flocculation of the abrasive grains. Therefore, it is preferable that an abrasive grain-containing dispersion is preliminarily prepared by dispersing abrasive grains therein at a higher concentration than that of an abrasive grain-containing dispersion which is actually employed, the abrasive grain-containing dispersion containing a higher concentration of abrasive grains being subsequently diluted with water to a desired concentration immediately before the actual use thereof for polishing. For example, in the case of a slurry for polishing an oxide film, a dispersion containing silica at a concentration of 30% by weight may be prepared at first and subsequently, diluted with water immediately before use to obtain a diluted dispersion having a volume which is three times as large as that of the initial volume. Even in a case where a dispersion containing a high concentration of abrasive grains is prepared at first and subsequently, diluted with water before use, the polishing apparatus according to this embodiment of the present invention can be suitably employed.

[0049] The slurry described above may further contain, as desired, any additives usually employed, such as an oxidizing agent, a surfactant, an oxidation inhibitor, a pH adjustor, etc. at a ratio which is usually employed.

[0050] As for the oxidizing agent, it is possible to employ H₂O₂, (NH₄)₂S₂O₈, K₂S₂O₈, iron nitrate, cerium ammonium nitrate, etc.

[0051] As for the surfactant, it is possible to employ dodecyl sulfonate, dodecyl benzene sulfonate, polyoxyethylene lauryl ether, fatty ester, polyoxyethylene alkylamine, etc.

[0052] As for the oxidation inhibitor, it is possible to employ BTA (benzotriazole), amine having carboxylic group, etc. As for the pH adjustor, it is possible to employ aqueous ammonia, KOH, nitric acid, citric acid, oxalic acid, succinic acid, etc.

[0053] In the polishing apparatus according to this embodiment of the present invention, the slurry employed therein is separated in advance into a first liquid and a second liquid, at least one of them containing an abrasive component, and these liquids are separately supplied, making it possible to avoid the slurry from being damaged in stability of quality. Moreover, since these two kinds of separately supplied liquid are uniformly mixed at a use-point, and the resultant mixed slurry is immediately employed for polishing, the effects of enhancing the polishing performance of slurry can be sufficiently exhibited. As a result, it is now possible to stably perform high performance polishing which is almost free from defects such erosion and scratches.

EXAMPLE 1

[0054] Next, one example for forming a Cu damascene wiring by using the polishing apparatus according to this embodiment of the present invention will be explained.

[0055]FIGS. 2A to 2C show cross-sectional views each illustrating a process for forming a Cu damascene wiring.

[0056] First of all, as shown in FIG. 2A, an interlayer insulating film 31 comprising a low-K material, etc. was deposited on the surface of a semiconductor substrate 30, thereby forming therein a groove having a depth of 3000 Å. Incidentally, the semiconductor substrate 30 may be a bulk substrate or an SOI substrate, and semiconductor elements (not shown) were integrally formed therein in advance. Then, a liner 32 constituted by Ta/TaN and having a thickness of about 300 Å was deposited on the substrate 30 by sputtering. Thereafter, a Cu layer having a thickness of about 7000 Å was deposited as a wiring material 33 on the substrate 30 by sputtering (seed layer) and plating method.

[0057] A redundant portion of the Cu layer as a wiring material 33 was removed as shown in FIG. 2B by CMP using the apparatus shown in FIG. 1. Thereafter, as shown in FIG. 2C, the liner 32 that was deposited on the interlayer insulating film 31 was removed by CMP to form a buried wiring in the groove.

[0058] On the occasion of this Cu-CMP procedure in this example, IC1000 (Rodel Nitta Co., Ltd.) was employed as the polishing cloth 13, and the slurry mixing vessel 17 made of plastic and having a radius of 20 mm and a height of 20 mm was fixed in place at the central portion of the non-polishing region of this polishing cloth 13, thereby constructing the polishing apparatus shown in FIG. 1. In the positioning of the slurry mixing vessel 17, the center of the slurry mixing vessel 17 was made coaxial with the center of the polishing cloth 13.

[0059] The slurry employed herein was formed of a mixture of two kinds of liquid, i.e. a first liquid which was a dispersion containing abrasive grains, and a second liquid which was a solution containing an oxidizing agent. This abrasive grain-containing dispersion was prepared by mixing in pure water 2% by weight of silica as a polishing grain, 1% by weight of quinaldinic acid as an oxidation inhibitor, and 0.4% by weight of a nonionic surfactant. The solution of oxidizing agent was prepared by dissolving 2% by weight of ammonium persulfate as an oxidizing agent in pure water.

[0060] In this polishing procedure, the turntable 11 was rotated at a speed of 100 rpm, during which two kinds of liquid were introduced dropwise into the slurry mixing vessel 17 at flow rate of 150 mL/min, respectively. Concurrently, while the top ring 14 holding a wafer 16 was rotated at a speed of 100 rpm, the top ring 14 was pressed down onto the polishing cloth 13 at a polishing load of 400 g/cm². Under these conditions, polishing was performed for 100 seconds to remove a redundant portion of the Cu layer, as shown in FIG. 2B.

[0061] Incidentally, the feeding flow rates of the first and second liquids, the rotational speeds of the turntable and the top ring, the polishing load can be suitably modified depending on the kind of polishing material, and of the chemical liquids, on the polishing conditions, etc.

[0062] Five seconds later, as measured from the initiation of the supply of these liquids, these two liquids were accumulated, as a uniform slurry which had been sufficiently mixed, up to the top of the slurry mixing vessel 17, thereby allowing these liquids to overflow from the slurry mixing vessel 17 and to be applied over the polishing cloth 13. Since this uniformly mixed slurry is enabled to spread over the polishing cloth 13 immediately before the polishing, it was possible to sufficiently derive the polishing performance which the slurry inherently had. More specifically, by using a conventional slurry (polishing rate: about 10000 Å/min; erosion: 300 Å or less) which was conventionally considered as having a high performance but having problems with respect to stability and life, it was possible to form a damascene wiring at a scale of mass production level.

[0063] The dependency of the polishing rate of Cu on the number of wafers is indicated by a curve “a” in FIG. 3. It is apparent from the curve “a” that when the apparatus of this example was employed, the non-uniformity of the polishing rate of Cu could be confined within ±250 Å/min or so even if 40 sheets of wafers were polished.

[0064] For the purpose of comparison, a Cu damascene wiring was formed in the same manner as described above by using the conventional apparatuses as shown in FIGS. 4 and 5. In the apparatus shown FIG. 4, two kinds of liquid were respectively fed onto the polishing cloth 13 and mixed together through the rotation of the turntable 11, thus rendering two kinds of liquid available for polishing. The apparatus shown in FIG. 5, on the other hand, illustrates an example wherein two kinds of liquid were supplied by using a T-shaped pipe. In this case, the tip ends of supply pipes 24 and 25 for feeding the liquids, respectively, were connected with the T-shaped pipe 51, thereby permitting a mixed slurry 52 to be dropped onto the polishing cloth 13. In this case, the flow rate of the mixed slurry 52 was the total of the supply flow rates of these two liquids.

[0065] In these conventional apparatuses, the polishing performance such as polishing rate and erosion was very poor in stability, making it sometimes impossible to perform polishing of Cu at all. The reason for this may be attributed to the fact that the two liquids were not sufficiently mixed, thus an insufficiently stable slurry was supplied to the polishing surface.

[0066] The dependency of the polishing rate of Cu on the number of wafers when the apparatus shown in FIG. 4 was employed is indicated by a curve “b” in FIG. 3. It is apparent from the curve “b” that when this conventional apparatus was employed, the polishing rate of Cu considerably fluctuated, and at the same time, gradually lowered as a whole as the number of wafers treated increased. Moreover, an erosion having a dimension of 500 Å or more was recognized on the surface of wafer after polishing. Even in the case where the apparatus of FIG. 5 was employed, almost the same results as those of the apparatus of FIG. 4 were obtained.

[0067] It was confirmed from this example that it was possible to perform a stable polishing when the apparatus of this example was employed.

EXAMPLE 2

[0068] In this example, a W damascene wiring was formed by using a slurry comprising a mixture of three kinds of liquid, i.e. an abrasive grain-containing dispersion as a first liquid, a solution of oxidizing agent as a second liquid, and a solution of a catalyst as a third liquid.

[0069] First of all, as shown in FIG. 2A, an interlayer insulating film 31 comprising of a low-K material, etc. was deposited on the surface of a semiconductor substrate 30, thereby forming therein a groove having a depth of 3000 Å. Incidentally, the semiconductor substrate 30 may be a bulk substrate or an SOI substrate, and semiconductor elements (not shown) were integrally formed therein in advance. Then, a liner 32 constituted by Ta/TaN and having a thickness of about 200 Å was deposited on the substrate 30 by sputtering. Thereafter, a W layer having a thickness of about 3500 Å was deposited as a wiring material 33 on the substrate 30 by sputtering.

[0070] A redundant portion of the W layer as a wiring material 33 was removed as shown in FIG. 2B by CMP using the apparatus shown in FIG. 1. The apparatus employed herein was the same as the apparatus shown in FIG. 1 except that a storage tank, a pump and a supply pipe, were additionally provided for the third liquid. Thereafter, as shown in FIG. 2C, the liner 32 that was deposited on the interlayer insulating film 31 was removed by CMP to form a buried wiring in the groove.

[0071] In this W-CMP procedure in this example, IC1000 (trade name; Rodel Nitta Co., Ltd.) was employed as the polishing cloth 13 in the same manner as in the aforementioned Example 1, and the slurry mixing vessel 17 made of plastic and having a radius of 20 mm and a height of 20 mm was screwed in place, at the non-polishing region of this polishing cloth 13, thereby constructing the polishing apparatus shown in FIG. 1. In the positioning of the slurry mixing vessel 17, the center of the slurry mixing vessel 17 was offset by a distance of about 5 mm from the center of the polishing cloth 13.

[0072] The slurry employed herein was prepared as follows.

[0073] Namely, a first liquid which was a dispersion containing abrasive grains was prepared by mixing in pure water 5% by weight of silica as a polishing grain, and 1% by weight of potassium dodecylbenzene sulfonate as a surfactant for enhancing the planarizing performance of the slurry. A second liquid which was a solution of an oxidizing agent was prepared by dissolving 1% by weight of hydrogen peroxide as an oxidizing agent in pure water. Further, copper sulfate was dissolved in pure water to obtain a 0.05 wt % aqueous solution thereof, thereby obtaining a third liquid containing Cu²⁺ion functioning as a catalyst for activating the hydrogen peroxide.

[0074] In this polishing procedure, the turntable 11 was rotated at a speed of 100 rpm, during which three kinds of liquid, i.e. the abrasive grain-containing dispersion, the oxidizing agent dispersion and the catalyst solution, were introduced dropwise into the slurry mixing vessel 17 at flow rate of 150 mL/min, respectively. Concurrently, while rotating the top ring 14 holding a wafer 16 at a speed of 120 rpm, the top ring 14 was pressed down onto the polishing cloth 13 at a polishing load of 400 g/cm², thereby removing a redundant portion of the W layer, as shown in FIG. 2B.

[0075] Five seconds later, as measured from the initiation of the supply of these liquids, these three kinds of liquid were accumulated, as a uniform slurry which had been sufficiently mixed, up to the brim of the slurry mixing vessel 17, thereby allowing these liquids to overflow from the slurry mixing vessel 17 and to be provided over the polishing cloth 13. It was possible in this slurry mixing vessel 17 to sufficiently mix potassium dodecylbenzene sulfonate in the slurry. Since this uniformly mixed slurry is enabled to be provided over the polishing cloth 13 immediately before the polishing, it was possible to sufficiently derive the polishing performance inherent to the slurry.

[0076] After the polishing was performed for two minutes (Just +30% over), the polishing rate of W was found to be about 3000 Å/min, and a damascene wiring of excellent quality exhibiting an erosion of 300 Å or less was obtained with high stability.

Example 3

[0077] The slurry mixing vessel functioning as a slurry mixing section for storing and mixing two kinds of liquid which have been separately introduced therein and for feeding a mixed slurry to the surface of the polishing cloth can be substituted by a recessed portion formed in the polishing cloth. FIG. 6 illustrates an example.

[0078] The polishing apparatus shown in FIG. 6 is substantially the same as the apparatus shown in FIG. 1 except that a slurry mixing recess 41 is provided, in place of the slurry mixing vessel 17, in the non-polishing region of the polishing cloth 13. The horizontal dimension of this recess 41 may be within the range of 10 mm to 60 mm in radius. If the size of this recess 41 is too small, it may become difficult to accommodate the two liquids being fed thereto, and to sufficiently carry out the mixing of them. On the other hand, if the size of the slurry mixing recess 41 is too large, it may become difficult to install the slurry mixing recess 41 within the non-polishing region of the polishing cloth 13, thereby obstructing the fundamental function of the polishing apparatus to polish a wafer. Further, in order to accommodate two liquids, and to enable these liquids to be sufficiently mixed together therein, the depth of the recess 41 should preferably be at least 1 mm. On the other hand, although there is no particular limitation with respect to the upper limit of the depth of the recess 41, the depth of the recess 41 should desirably be limited, unless the surface of the turning table 11 is specifically protected by a suitable means, to such an extent that the recess 41 is not deep enough to pass through the polishing cloth 13, in order to avoid corrosion of the turntable 11.

[0079] Further, as for the configuration of the recess 41, although there is no particular limitation, the configuration of the recess 41 should preferably be cylindrical for the same reason as set forth in the explanation of the aforementioned slurry mixing vessel.

[0080] This recess 41 can be formed in the polishing cloth 13 by dimpling work or recessing work, for instance. As for the polishing cloth 13, it is possible to employ a 2-ply laminate structure consisting of SUBA400 (trade name; Rodel Nitta Co., Ltd.) and IC1000 (trade name; Rodel Nitta Co., Ltd.) for instance. In this case, the recess 41 can be formed by cutting a predetermined portion of the laminate structure, which corresponds to the non-polishing region, into a desired configuration by using a cutter or a mold before or after laminating these sheets.

[0081] There is no particular limitation with respect to the location at which the slurry mixing recess 41, as long as the location is confined within the non-polishing region and suited for receiving and accommodating the aforementioned two kinds of slurry. Further, the center of the slurry mixing recess 41 is not necessarily aligned with the center of the polishing cloth 13.

[0082] By using the polishing apparatus shown in FIG. 6, the polishing of the oxide film (SiO₂ film) having a step portion originating from an underlying wiring pattern was performed. As for the polishing cloth 13 to be employed herein, a 2-ply laminate polishing cloth consisting of SUBA400 and IC1000 was prepared. The central portion of this laminate polishing cloth was worked by a cutter, to form a cylindrical recess having a radius of 40 mm and a depth of 1 mm.

[0083] As for the slurry employed herein, an abrasive grain-containing dispersion wherein 0.5% by weight of ceria particles was dispersed as abrasive grains in pure water, as well as an additive-containing solution wherein 30% by weight of polycarboxylic acid-based surfactant was dissolved in pure water were employed as a first liquid and a second liquid, respectively.

[0084] In this polishing procedure, the turntable 11 was permitted to rotate at a speed of 100 rpm, during which the aforementioned two liquids were introduced dropwise into the slurry mixing recess 41 at a flow rate of 150 mL/min, respectively. Concurrently, while rotating the top ring 14 holding a wafer 16 at a speed of 107 rpm, the top ring 14 was pressed down onto the polishing cloth 13 at a polishing load of 500 g/cm², thereby polishing the oxide film.

[0085] When the polishing was performed for two minutes, the polishing rate of the SiO₂ film was found about 3000 Å/min or more, thus making it possible to planarize the initial stepped portion having a height of 6000 Å. The erosion on the surface of oxide film after the polishing was confirmed to be limited to 500 Å or less.

[0086] Although the embodiments of the present invention have been explained taking several of them as examples, the present invention should not be construed as limited to such embodiments. For example, the slurry mixing vessel and the slurry mixing recess, both employed as a slurry mixing section, may be suitably selected in combination with the slurries which require a separate storage as mentioned above. In any combination thereof, it is possible to realize the effects which make it possible to perform a stabilized polishing with a sufficiently large polishing rate.

[0087] As explained above, according to one embodiment of the present invention, it is possible to provide a polishing apparatus which is capable of polishing any desired layer of a treating substrate at a sufficiently large polishing rate while making it possible to extremely minimize the generation of defects, such as erosion and scratches of the treating substrate, and also making it possible to retain the stability and life of slurry without necessitating the provision of an auxiliary supply facility. Further, according to another embodiment of the present invention, it is possible to provide a polishing method which is capable of polishing any desired layer of a treating substrate at a sufficiently large polishing rate while making it possible to extremely minimize the generation of defects such as the erosion and scratches of the treating substrate and also making it possible to retain the stability and life of slurry. Moreover, according to a further embodiment of the present invention, it is possible to provide a method of manufacturing a semiconductor device provided with a damascene wiring of high performance.

[0088] The present invention is very useful in the formation of a damascene wiring of Cu, W, Al, etc., which is designed to be mounted on a DRAM or a high-speed logic LSI, and therefore, the present invention is very valuable from an industrial view point.

[0089] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention is its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

What is claimed is:
 1. A polishing apparatus comprising: a turntable having a polishing region where a treating substrate moves relative thereto, and a non-polishing region surrounded by said polishing region; a substrate holder holding said substrate, thereby enabling said substrate to press-contact with a polishing surface located within said polishing region; a first supply pipe feeding a first liquid; a second supply pipe feeding a second liquid; and a slurry mixing vessel disposed above said turntable within said non-polishing region and away from the tip ends of said first supply pipe and said second supply pipe, said slurry mixing vessel storing and mixing said first and second liquids to obtain a mixed slurry and to feed said mixed slurry onto said polishing surface.
 2. The polishing apparatus according to claim 1, wherein said slurry mixing vessel is secured to said turntable through a polishing cloth adhered to said turntable.
 3. A polishing method comprising: positioning a treating substrate held by a substrate holder over a turntable so as to enable said treating substrate to press-contact with a polishing region of a polishing surface of said turntable, said polishing surface having said polishing region where said treating substrate moves relative thereto, and a non-polishing region surrounded by said polishing region; introducing a first liquid and a second liquid into a slurry mixing section disposed at said non-polishing region of said polishing surface, at least one of said first and second liquids containing an abrasive component; and applying a mixed slurry comprising said first and second liquids which have been mixed together in advance in said slurry mixing section to said polishing surface while rotating said turntable to enable said treating substrate to move relative to said polishing region, thereby polishing said treating substrate.
 4. The polishing method according to claim 3, wherein said mixed slurry comprising a mixture of said first and second liquids overflows from said slurry mixing section, thereby feeding said mixed slurry onto said polishing surface.
 5. The polishing method according to claim 3, wherein said slurry mixing section is a slurry mixing vessel fixed in place to a polishing cloth adhered to said turntable.
 6. The polishing method according to claim 3, wherein said slurry mixing section is a recessed portion formed in a polishing cloth adhered to said turntable.
 7. The polishing method according to claim 3, wherein said first liquid comprises abrasive grains and water; while said second liquid comprises an oxidizing agent and water.
 8. The polishing method according to claim 3, wherein said first liquid comprises abrasive grains and water; while said second liquid is water diluting said first liquid.
 9. The polishing method according to claim 3, wherein said first liquid and said second liquid are a combination of two liquids selected from the group consisting of an abrasive grain-containing dispersion liquid, a solution of an oxidizing agent, and a solution of a catalyst.
 10. The polishing method according to claim 3, wherein said first liquid comprises abrasive grains and water; while said second liquid comprises a surfactant and water.
 11. A method for manufacturing a semiconductor device comprising: forming an insulating film above a surface of a semiconductor substrate; forming a recessed portion in said insulating film; depositing a conductive material in said recessed portion as well as above said insulating film, to form a conductive layer; and removing the portion of said conductive material that has been deposited above said insulating film outside said recessed portion to leave said conductive material in said recessed portion; wherein at least part of said conductive material deposited above said insulating film is removed by: positioning said semiconductor substrate held by a substrate holder over a turntable so as to enable said semiconductor substrate to press-contact with a polishing region of a polishing surface of said turntable, said polishing surface having said polishing region where said semiconductor substrate moves relative thereto, and a non-polishing region surrounded by said polishing region; introducing a first liquid and a second liquid into a slurry mixing section disposed at said non-polishing region of said polishing surface, at least one of said first and second liquids containing an abrasive component; and applying a mixed slurry comprising said first and second liquids which has been mixed together in advance in said slurry mixing section to said polishing surface while rotating said turntable to enable said semiconductor substrate to move relative to said polishing region, thereby polishing said conductive material.
 12. The method according to claim 11, wherein said mixed slurry comprising a mixture of said first and second liquids overflows from said slurry mixing section, thereby feeding said mixed slurry onto said polishing surface.
 13. The method according to claim 11, wherein said slurry mixing section is a slurry mixing vessel fixed in place to a polishing cloth adhered to said turntable.
 14. The method according to claim 11, wherein said slurry mixing section is a recessed portion formed in a polishing cloth adhered to said turntable.
 15. The method according to claim 11, wherein said conductive material comprises a Cu layer disposed through a liner layer.
 16. The method according to claim 15, wherein said first liquid comprises abrasive grains and water; while said second liquid comprises an oxidizing agent and water.
 17. The method according to claim 11, wherein said conductive material comprises W.
 18. The method according to claim 17, wherein said first liquid and said second liquid are a combination of two liquids selected from the group consisting of an abrasive grain-containing dispersion liquid, a solution of an oxidizing agent, and a solution of a catalyst.
 19. The method according to claim 11, wherein said conductive material comprises Ru or a Ru compound.
 20. The method according to claim 19, wherein said first liquid is an aqueous solution containing a high concentration of a cerium compound (IV); while said second liquid is water for diluting said aqueous solution. 